Organic-inorganic perovskite solar cells are typically prepared in a single bandgap configuration, where an absorber layer (ABX3, A=CH3NH3(MA); B═Pb, Sn; and X═Cl, Br, I) is sandwiched between an electron transport layer (ETL) and a hole transport layer (HTL). Following significant effort in optimizing interface layers to control the carrier dynamics, power conversion efficiencies (PCEs) for this design, for a single cell, have surpassed 20%. In addition, due to the toxicity of lead in the absorber layer, lead-free tin halide perovskite solar cells have gained tremendous importance. However, lead-free cells do not exhibit such high photovoltaic performances (e.g., less than 7%) due to chemical instability.
The tunable bandgap of methylammonium-lead-halide has also led researchers to construct multijunction tandem cells which aim to maximize the solar irradiative spectrum. In these tandem cells, the perovskite layer can be integrated with crystalline silicon (c-Si) and copper indium gallium selenide (CIGS). However, the tandem cell requires complex electrical coupling and interconnection between the perovskite sub-cells, which generates electron-hole recombination centers.